Q: Can I install an ssd and his system from MacBook Pro mid 2010 on a Mac Pro mid 2009

Since both Macs are able to run the latest version of OS X and you want to move the SSD to an older rather than newer Mac, it should work. I assume that by saying you "ordered a case to install the ssd in the machine" you mean connecting it via USB rather than internally, which would be an excellent test.

If it works, I'd suggest running the combo update for whichever OS is on the SSD once it's installed in the older Mac.

What do you mean by case?

Running via a USB o the Mac will results in somewhat sluggish operation since the silver tower Mac Pros only have USB 2 ports.

You can purchase a sled that accepts a 2 1/2 inch drive that replaces one of your original sleds

http://eshop.macsales.com/item/Other%20World%20Computing/MMP35T25/

A Mac with an Intel processor can boot from either an FireWire or USC connection. The older Macs with an Power PC processor can only boot from FireWire.